Tubular prostheses or “stents” are often implanted within blood vessels, for example, within the coronary and carotid arteries, for treating atherosclerotic disease that may involve one or more stenoses. Stents generally have a tubular shape capable of assuming a radially contracted condition to facilitate introduction into a patient's vasculature, and an enlarged condition for engaging the vessel wall at a treatment location. In its contracted condition, the stent may be placed on or in a delivery device, such as a catheter, percutaneously introduced into a patient's vasculature and advanced to a target treatment location, such as a stenosis, occlusion, or other lesion within a blood vessel. Once at the treatment location, the stent may be deployed and expanded to its enlarged condition, thereby engaging the wall of the vessel and substantially anchoring the stent in place.
Plastically deformable tubular stents have been suggested that are initially provided in their contracted condition, and placed over a balloon on a delivery catheter. At the treatment location, the balloon is inflated to plastically deform the stent until it is expanded to its enlarged condition. Thus, the stent may be expanded to any size within a specified range to ensure that the stent substantially engages the wall of the vessel.
Self-expanding tubular stents have also been suggested that are biased to assume their enlarged condition but may be radially compressed to a contracted condition. The stent may be mounted to a delivery device and constrained in a contracted condition during delivery, for example, by an overlying sheath. At the treatment location, the stent may be released, for example, by retracting the overlying sheath, the stent automatically expanding to its enlarged condition to engage the vessel wall.
In addition to tubular stents, coiled-sheet stents have been suggested. A flat sheet is rolled into a spiral shape having overlapping inner and outer longitudinal sections that defines a contracted condition. The coiled-up sheet may be biased to at least partially unroll to assume an enlarged condition, and/or may be unrolled and radially expanded using a balloon. The coiled-sheet stent may have a lattice-like structure and a plurality of fingers or teeth along the inner longitudinal section for engaging openings in the lattice. Once the coiled-sheet stent is expanded at a treatment location, the fingers on the inner longitudinal section may engage corresponding openings in the lattice to lock the stent in the enlarged condition.
Coiled-sheet stents may provide enhanced anchoring within the blood vessel because the size of the fully expanded stent may be more precisely controlled. A conventional rectangular lattice, such as that disclosed in U.S. Pat. No. 5,443,500 issued to Sigwart, however, may result in a coiled-sheet stent that is more rigid transverse to its longitudinal axis than desired, i.e., that may not bend as easily as desired, particularly when being delivered through tortuous anatomy.
Accordingly, it is believed that a stent that provides enhanced flexibility would be considered useful.